An Updated Classification of the Recent Crustacea

cies of crab (Manning and Felder, 1996). An ovigerous
hermit crab (probably genus Pygmaeopagurus)
with a shield length of only 0.76 mm taken
from dredge samples in the Seychelles (McLaughlin
and Hogarth, 1998) might hold the record for decapods,
and of course much smaller crustaceans exist.
Tantulocarids, recently discovered parasites found
on other deep-sea crustaceans, are so small that
they are sometimes found attached to the aesthetascs
of the antennule of copepods; the total body
length of Stygotantulus stocki is only 94 �m ‘‘from
tip of rostrum to end of caudal rami’’ (Boxshall and
Huys, 1989a:127). In terms of biomass, that of the
Antarctic krill Euphausia superba has been estimated
at 500 million tons at any given time, probably
surpassing the biomass of any other group of
metazoans (reviewed by Nicol and Endo, 1999). In
terms of sheer numbers, the crustacean nauplius
has been called ‘‘the most abundant type of multicellular
animal on earth’’ (Fryer, 1987d). Crustaceans
have been found in virtually every imaginable
habitat (see Monod and Laubier, 1996), have been
mistaken for molluscs, worms, and other distantly
related animals, and continue to defy our attempts
to force them into convenient taxonomic groupings.
Indeed, there is still considerable debate over
whether the group is monophyletic (see below).
Not surprisingly, the history of crustacean classification
is a long and convoluted one. A summary
of that history is well beyond the scope of this paper,
and the reader is referred to the following publications
as some of many possible starting points:
Schram (1986); Fryer (1987a, c); Dahl and Strömberg
(1992); Spears and Abele (1997); Rice (1980);
Schram and Hof (1998); Monod and Forest (1996);
and papers in the edited volumes The Biology of
Crustacea (1982–1985; D. E. Bliss, editor-in-Chief)
(especially volume 1); Crustacean Issues (F. R.
Schram, general editor); Arthropod Fossils and
Phylogeny (G. D. Edgecombe, editor); Traité de
Zoologie (P.-P. Grassé, series editor; J. Forest, crustacean
volumes editor); and the Treatise of Invertebrate
Paleontology (R. C. Moore, editor) (a revision
of this last work is currently underway). Despite
the long history of studies on Crustacea, in
many ways, we are just beginning our journey. New
and significant finds continue to delight and surprise
the student of the Crustacea. In the last two
decades, the newly discovered taxa Remipedia,
Tantulocarida, and Mictacea, as well as beautifully
preserved fossils from the ‘‘Orsten’’ fauna of Sweden,
are some of the more obvious examples. Another
striking example of how little we know about
crustaceans is the relatively recent discovery of an
entirely new phylum of animal life, the Cycliophora
(Funch and Kristensen, 1995; Winnepenninckx et
al., 1998), found living on the mouthparts of the
Norway lobster Nephrops norvegicus, a species of
commercial importance that is encountered often in
European restaurants.
The 1982 classification of the Recent Crustacea
by T. E. Bowman and L. G. Abele, in turn based to
a large extent on that of Moore and McCormick
(1969), was a benchmark compilation that has
been of tremendous use to students of the Crustacea.
In that classification, the extant crustaceans
were divided among 6 classes, 13 subclasses, 38 orders,
and 652 families. Although it was recognized
by Bowman and Abele and other workers in the
field, even at the time of publication, that the classification
was intended to be little more than a stopgap
measure, it has continued to be employed in
many major treatments of crustaceans (e.g., Barnes
and Harrison, 1992; Young, 1998) and has widely
influenced the study of crustaceans since its appearance.
Subsequent to the appearance of the
Bowman and Abele (1982) classification, a large
number of new families and even some higher level
taxa have been described. Indeed, our current list
includes 849 families, an increase of 197 families
over the Bowman and Abele (1982) classification.
Thus, an argument could be made that an updated
classification is warranted on the basis of the increased
number of new families alone. A more
compelling reason is that several major treatises
have appeared that offer substantially different arrangements
of those taxa and that many exciting
areas of phylogenetic research and improved methodology
have contributed significantly to our understanding
of the relationships within the Crustacea
and of the Crustacea to other arthropod
groups.
While attempting to arrange the collections at the
Natural History Museum of Los Angeles County,
the second largest collection of crustaceans in the
United States, we decided to update the Bowman
and Abele (1982) classification by simply inserting
the taxa described since that time. This proved to
be a more difficult task than we originally envisioned.
In part this was because the number of new
taxa was larger than we first thought. And, in part,
it was because there have been so many suggestions
for new arrangements and groupings of crustacean
assemblages, and we wanted to reflect some of the
recent thinking in crustacean phylogeny in the arrangement
of our museum’s collection. At about the
same time, we announced a World Wide Web product
(http://www.nhm.org/cbs/) called the Crustacean
Biodiversity Survey (Martin, 1996). The Survey
was designed to allow workers from anywhere
in the world to add information at a variety of levels
to a database on crustacean biodiversity. The
currently proposed classification is one result of
that survey.
Lines have to be drawn at certain times in order
to attain some level of completion. We received the
suggestion from several workers to take the classification
down to the level of subfamily; one worker
even suggested we include a list of all known genera
for each family. Others suggested that we provide
a clear diagnosis and/or characters that distinguish
each taxon or at least each major clade. Although
these additions would undoubtedly be extremely
helpful, for what we hope are obvious reasons, we
2 � Contributions in Science, Number 39 General Introduction